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If you have a variable speed blower motor, a bad motor speed controller can keep it running even with the key out of the ignition. See this post on blower motor controllers. https://ricksfreeautorepairadvice.com/blower-motor-wont-shut-off/
Like all electronic devices, a blower motor must have power and ground in order to function. A blower motor that continues to operate when the switch is turned off still has both power and ground present when it shouldn't. Assuming this vehicle has the manual HVAC system (rather than automatic), the blower motor should be disabled by interrupting the power supply circuit to the blower. The ground side of the blower circuit will always have a ground path through the function selector switch assembly. Power is supplied to the blower motor using a blower relay. Relays have a "control side" which also require both power and ground as well as an "output side" which has power and a path to whatever component it is that the relay operates. On this vehicle the control side of the blower relay is always grounded and the power side is only energized when the function selector switch assembly is moved away from the "OFF" position. A short-to-power in this circuit within the function selector switch assembly could provide power at all times and cause the blower to never turn off. Alternatively if we assume the control side is working normally and turning off when it should, the output side of the relay should never provide power to the component. That is unless the contacts within the relay have a short-to-power condition in which case the blower would receive power at all times. To summarize, I would suspect either the function selector switch assembly is internally shorted or the blower relay is stuck in the "ON" position. You can read more here: https://www.yourmechanic.com/article/how-to-buy-a-good-quality-heater-blower-motor
The relay in your blower motor is stuck on, there is a TSB for this issue. Replace the blower motor resistor and you'll be back in business. How does the resistor get power if the fuse is pulled? Replacing the resistor will cure both problems. TSB is a technical service bullitin seen below Subject:HVAC Blower Motor May Run Continuously After Vehicle is Turned Off (Replace Blower Resistor Relay)Models:2004 Chevrolet Avalanche, Silverado, Suburban, Tahoe, TrailBlazer, TrailBlazer EXT2004 GMC Envoy, Envoy XL, Sierra, Yukon, Yukon XLwith Manual Control HVAC (RPO CJ3)Built Prior to August, 2003
If you mean that the blower motor runs even after turning the key off...the resister to the blower motor has to be bad to allow this continuosly get current...:)
Hello and welcome. this is caused by the blower resistor also called a blower control module. you will need to replace the blower resistor. it is mounted under the passenger side of dash next to the blower motor
Run's continuously ? High speed , low , med 1,2, 3 . ????
Probably the high speed relay contact's stuck closed . The fuse for the high blower is hot at all times , low blower fuse is hot only with key on. It sparks becaused the motor turns on . If it had a short the fuse would blow . The blower motor relay is part of the resistor pack near the blower motor .
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